1. Technical Field
The present invention relates to a storage medium storing image processing program, image processing apparatus, and image processing method for processing image data containing graphics and images, and particularly to a storage medium storing image processing program, image processing apparatus, and image processing method designed to be able to process image data without impairing the meaning of lines contained in the image data.
2. Related Art
In general, architectural and engineering designs or plans are drawn on paper or the like to communicate them to people, and enable manufacturers or building constructors to understand contents of the designs or plans and to produce products or build buildings according to the designs or plans. Recent improvement in technology has made the design drawings available electronically with the use of CAD (Computer Aided Design) technology or the like.
Preparation of drawings with the use of CAD technology has become rather common, and anyone is allowed to refer to or to print out any desired drawing at any time through a centralized management of CAD-prepared drawings with the use of a graphic management system or the like.
The CAD-prepared drawing can be viewed or printed out not only in its original size but also in an enlarged or reduced size. For example, a design drawing prepared in A1 size can be printed out in A3 size with a necessary processing to reduce the scale of the original design drawing to one fourth. In some cases, the drawing is displayed on a device after converting the resolution to match the display ability of the device.
Lines such as straight lines and curved lines are drawn in a design drawing such that they can be discriminated by differing the widths or patterns of the lines. These lines often have their own meanings. In architectural drawings, for example, architectural materials to be used and where it is placed in the whole architectural structure are differentiated by differing the width of the lines (hereafter to be referred to as the “line width”).
Similarly, a document prepared in a common office environment sometimes gives meanings to lines contained therein. On the other hand, improvement in the performance of printers and printer drivers has made it possible to print a plurality of pages on a single sheet of paper (“N-up print”) for the purpose of saving paper or protecting the nature and environment. If the N-up print is used to print the document, it is required to reduce the size of each page of the document so that the meanings of the lines may be lost.
This has required the user to refer to the original electronic file to check the line widths that the lines originally have.
Thus, there has conventionally been a problem that, due to the lack of understanding the importance of differentiating the meanings of lines by giving the lines different line widths, offhand reduction of the line widths was likely to be performed, resulting in that all the lines seemed to have an identical line width.
FIGS. 9A and 9B show an example in which the number of different line widths is reduced as the result of resolution conversion (conversion from high to low resolution) according to a conventional technique.
FIG. 9A shows a drawing drawn at 600 dpi (dot per inch), or at its original scale, in which three different lines are shown. A first line has a line width of 1 dot (“1”). A second line has a line width of 3 dots (“3”), and a third line has a line width of 5 dots (“5”).
FIG. 9B shows the line widths that these three different lines take when the drawing resolution is reduced to ⅓, or 200 dpi.
When the resolution is reduced to ⅓, or 200 dpi, the line having the line width “1” as shown in FIG. 9A is represented as a line having the minimum line width, i.e., the line width “1” in FIG. 9B.
The line having the line width “3” as shown in FIG. 9A is represented as a line having the line width “1”, that is one third of the line width “3” in FIG. 9B. The line having the line width “5” as shown in FIG. 9A is represented as a line having the line width “2” in FIG. 9B, that is obtained by dividing 5 by 3 and rounding up the value after the decimal point to the integer “2”.
As seen the foregoing, although these three lines are represented as having three different line widths in the drawing before the resolution conversion as shown in FIG. 9A, the number of different line widths has been reduced to two in the drawing after the resolution conversion as shown in FIG. 9B, which results in that lines having the line widths “1” and “3” before the convention are treated as a line having the same line width.
If lines with different line widths are treated as lines having an identical line width, as in the example shown above, the meanings of these lines will be lost and thus the drawing reduced in size will become useless.